Hydroformed metal hull

[jimrudholm]

The James F. Lincoln Arc Welding Foundation published the book, "Design for
Welding" in 1948. It was reprinted in 1956. One of the articles, "The Small
Sailing Yacht Adapted for Arc Welding Construction" showed an experiment that
hydroformed a pair of steel dinghy hulls. The author also proposed a design for
a 37' sailing hull with material and cost estimates.
I made a model using this technique of the 'Helen B. Thomas', a knockabout
schooner built in Boston in 1902. Photos are here:
http://picasaweb.google.com/jimrudholm/SailboatHull#
It was pressurized with an oil hand pump. The extra heavy deck and keel was to
keep the deck from deforming.
The author stated that the elongation necessary was 12%, steel can go 20-30%.
Aluminum would work,too.
Has anyone tried this technique?

[frank smith]

Originally Posted by jimrudholm

The James F. Lincoln Arc Welding Foundation published the book, "Design for
Welding" in 1948. It was reprinted in 1956. One of the articles, "The Small
Sailing Yacht Adapted for Arc Welding Construction" showed an experiment that
hydroformed a pair of steel dinghy hulls. The author also proposed a design for
a 37' sailing hull with material and cost estimates.
I made a model using this technique of the 'Helen B. Thomas', a knockabout
schooner built in Boston in 1902. Photos are here:
http://picasaweb.google.com/jimrudholm/SailboatHull#
It was pressurized with an oil hand pump. The extra heavy deck and keel was to
keep the deck from deforming.
The author stated that the elongation necessary was 12%, steel can go 20-30%.
Aluminum would work,too.
Has anyone tried this technique?

dont know about boats , but there is a lot of hydro forming going on today .
I can see no reason that a why cannot be built just like a car .

[matt H.]

I guess would be pretty easy quick way of forming metal
concrete form , sheet metal , and water , explosives .

the trick would be to sand wedge two different metals or materials mass , possibly for buoyancy and most definitely for the sound of the material

as for strength it could be pretty tough ,

example
two pieces from aluminum cans and some JB weld can be not only strong but it is also acoustically forgiving as has low vibration or acoustic resonance

finding or creating an epoxy mix or structural combination of different bonds and or corrugate epoxy grain that can float the metal sand wedge and still remain thin and strong would be key

things to hope for, molecular fusion bonds between metals and plastics and possible ceramics

[Munter]

There was a thirty foot plus boat built in australia in that method some time in the early nineties. Aus sailing did an article on it including a photo at the moment of detonation! Can't tell you any more though.

[jimrudholm]

The technique built two dinghy hulls, deck-to-deck, with no mold. Black pipe, 3/4", was bent to the shape of two keels and false common gunwhales. Timber columns on 12" centers braced the keels, another set for the gunwhales. Four 18 ga. sheets were cut and welded, resulting in a shape that looked like a half-inflated football (American) bladder. Then water pressure at 100 psi expanded the sheets to the proper shape. A rough estimate of the pressure required was found with this formula: P = t x 40,000 x 2/B. P = pressure in psi, t = thickness of sheet, 0.050", and B = rough diameter of 40". 40,000 is the yield strength of the steel sheet.
After inflation, the two hulls were cut apart at the sheer and C section gunwhales welded. The pointed stern was cut off and a transom welded on.
My model used the extra heavy deck to keep all the stretching in the hull sheets.

[Wynand N]

Originally Posted by Munter

There was a thirty foot plus boat built in australia in that method some time in the early nineties. Aus sailing did an article on it including a photo at the moment of detonation! Can't tell you any more though.

Seen those photos myself. A concrete former (mold) was made in the ground, alu plate laid, explosives added, lid on and bang - out comes a perfectly fair hull.

It was an American publication that covered this Australian thing and if I remembered correctly, it was in the late 80's...

[Munter]

I'm happy to be corrected on all those fronts Wynand!

[jimrudholm]

Wynand N,
I get a photo of a pretty blond and a list of shopping sites when I click on your website.

Jim

[jonr]

The Tracker Avalanche (a bass boat) was supposedly hydroformed aluminum. I doubt it was explosive hydroforming though.